Bell Siphon Need to Cycle 24/7?

[Chris Moreno]

I'm a Student Sustainability Coordinator at the junior college I'm attending and I'm working on my first aquaponics system. It's going to be an outdoor system in our french biodynamic garden on campus. We're trying to get it up and cycling asap because Earth Week is right around the corner. We'll be using a solar panel with a charge controller to charge a battery which will power our water pump. I'm not a solar guy so I'm hoping my co-worker can run our AC water pump off a battery.

Does the system need to cycle throughout the night? What will happen if it doesn't?

[TCLynx]

An inverter will be needed to run an AC pump from the battery system.

If you do not run the pump at night, there will be no filtration for the fish for the night.  And if you don't have any sort of supplemental aeration running for the system, there will be no aeration for the fish over night.  If you run very very minimal fish loads and the water volume is big enough, you might get away with not running the pumps overnight but be aware that in a system with a heavier fish load, going without any pumping, filtration or aeration over night during warm weather could mean all fish dead in the morning.  Careful monitoring of water quality and dissolved oxygen levels just before pumping is turned back on in the morning could become critical.

[Rob Torcellini]

TC is right on the money.  I run a fairly low density in my system and shut off the pump at night.  When the water is cold, I don't aerate it, but during the summer, I keep a small pond pump running in the tank with a sprayer to keep the DO levels higher.

[Chris Moreno]

Thanks for the reply TC!

We found some DC water pumps!

Looks like we'll definitely keep it running throughout the night. We have a battery large enough to keep the pump going.

TCLynx said:

An inverter will be needed to run an AC pump from the battery system.

If you do not run the pump at night, there will be no filtration for the fish for the night.  And if you don't have any sort of supplemental aeration running for the system, there will be no aeration for the fish over night.  If you run very very minimal fish loads and the water volume is big enough, you might get away with not running the pumps overnight but be aware that in a system with a heavier fish load, going without any pumping, filtration or aeration over night during warm weather could mean all fish dead in the morning.  Careful monitoring of water quality and dissolved oxygen levels just before pumping is turned back on in the morning could become critical.

[Chris Moreno]

Thanks for the reply Rob! Looks like we'll be running the pump all night.

Rob Torcellini said:

TC is right on the money.  I run a fairly low density in my system and shut off the pump at night.  When the water is cold, I don't aerate it, but during the summer, I keep a small pond pump running in the tank with a sprayer to keep the DO levels higher.

[Chip Pilkington]

You might consider a DC air pump for night aeration. They draw much less current than the water pump and can easily run off the same battery at night. You could always add an additional battery if required. This is a common strategy for backup when AC goes down.

If you do shut down the water pump at night, you might dig a little deeper into the practice. Not everyone drills a small drainhole in the base of the standpipe, so potentially, some or all of your GB's could remain flooded or partially flooded all night. Some folks are ok with this, others prefer they be drained when the pump is off. Once again, you might consider what's best for your system in relation to climate (temps), fish and plant species, etc.

[Matthew Smith]

Hello Chis,

 

I am planning on building a solar powered aquaponics system next spring. How has yours been running so far? Any luck?

A friend of mine can get a 250 Watt panel and I have a local source for used car batteries. I am hoping with a decent DC pump I'll be able to get the system up and running. What do you think?

 

Thanks, Matt

[TCLynx]

Matthew,

    You will probably also need a charge controller.  And used car batteries are not the best choice for running AP systems since deep cycling car batteries tends to shorten their life a lot and used ones are already probably in less than great shape.

A 250 watt solar panel would be sort of like putting a slow charger on a car battery when the sun is shining on the panel. (As in this is great if you want to keep stored batteries topped up but won't charge batteries very quickly if they are drained down, which they will be if you just tried to run the pump all night from them, and probably won't provide enough juice to charge the batteries as well as run the pump at the same time.) If you are running much more than a tiny aquarium system (which I don't advise doing outdoors since it is too small to be temperature stable) I really don't think there is a chance the system could run totally off just the solar panel, car batteries and a DC pump for much more than a couple afternoons.

[Matthew Smith]

Okay, thank you TCLynx

 

My system will consist of about 2,000 liters. Do you think two 250 Watt panels and a larger battery would do the trick?

 

I look into getting a charge controller.

 

All the best, Matthew

[Rob Torcellini]

You need to figure out how many watts your pumps are and calculate the total amount of storage you will need.  Most likely you will not have enough power.  Also, you will not want to run on car batteries as they are not design to be drained to low.  You will need to get a deep cycle battery.  A charge controller to be used to get the power from the panels into the batteries, and another charge controller to go between the batteries and your pumps.  (sometimes these are together on low end controllers).  If you don't use a charge controller for your pumps, you will quickly destroy the batteries as you can over-drain them.  Typical rule of thumb on solar systems for costing the components.  1/3 is the panels, 1/3 is the batteries, and 1/3 is the charge controllers.

For my system, I need an overall average 100 watts to run the pumps day & night.  Total charging power needs to be calculated during the amount of light the panels get during the worst season (the winter) and to have enough charge stored for cloudy days.  Here in New England, we have a long winter and a lot of clouds.  A system for my setup to run the 100 watts is 8 panels (245watts each), 4 deep cycle batteries, 2 charge controllers, and one smaller charger controller for the 12V out.  Circuit breaker panels, racks and misc cabling cost about 7 grand. 

Or, I can run $200 worth of extension cables to the greenhouse. 

[Matthew Smith]

Rob,

Wow! That is quite a reality check for me.

 

How big is your aquaponics system and are you using your PV system for more than just pumping water and air?

Thanks so much for your response!

Matthew

 

 

[Rob Torcellini]

geodesic dome

[TCLynx]

Thanks Rob.  Cause I couldn't have given nearly so good an answer since I haven't tried to speck out a Solar power system yet.  (I have to buy a tractor first.)